| 摘要 |
PURPOSE:To improve reliability of a backup power supply in an electronic equipment having the backup power supply in addition to a main power supply. CONSTITUTION:A power supply switching circuit 1 is constituted by providing a transistor Q1 which becomes conductive when the potential difference between main power supply voltage and backup power supply voltage is increased to a predetermined level VF2 or more, transistor Q2 which becomes conductive arrompanying the energization of the transistor Q1 to supply a backup power supply voltage EB to an output terminal T and a bleeder resistor r3 for making the energization of the transistor Q2 steep. |
